1. Field of the Invention
The present invention is directed to a method for proofing a rotogravure cylinder, and in particular to such a method which can be undertaken at the plant of the manufacturer of the rotogravure cylinder without the necessity of installing the cylinder in the press in which it is to be actually used.
2. Description of the Prior Art
The use of high strength electrically fields to assist in the transfer of ink from a rotogravure cylinder to a moving web of paper is known in the art. Various theories exist as to why the application of such fields is effective for this purpose, however, it is believed that the ink molecules carry a charge or have a plurality and are therefore caused to move in one direction by a properly oriented electric field.
In a conventional rotogravure press section, which may have a number of rotogravure printing cylinders over which a continuous web of paper is moved, access to both sides of the web is readily available. Electrodes of opposite plurality can thus be easily placed on opposite sides of the web, so that the necessary electric field can be generated through which the web is moved. A problem in the art exists in generating a similar field in an apparatus prior to installation of the rotogravure cylinder in the actual press section in which it is to be used. For example, manufacturers of rotogravure cylinders conduct a so-called proofing operation before sending the rotogravure cylinder out of the manufacturing facility to the ultimate user. Such manufacturers do not have, and could not economically afford, a complete rotogravure press section in which to test or proof the rotogravure cylinders before sending the cylinders to a customer. It is therefore a problem in the art to provide a means for generating an electric field in a rotogravure cylinder which is completely wrapped with a proofing sheet so that a proofing operation, aided by a high strength electric field for ink transfer, can be conducted prior to shipment of the cylinder.